Descending counter



March 14, 1950 B. E. PHELPS 2,500,294

DESCENDING COUNTER xNvENToR BYRUN E. PHE/.PS

ATTORNEY B. E. PHELPS DESCENDING COUNTER March 14, 1950 4 Sheets-Sheet 2 Filed Aug. 13, 1947` INVENTOR BYRON E. PHELPS BY l ATTO R N EY DESCENDING COUNTER March 14, n 195o Filed Aug. 15, 1947 4 Sheets-Sheet 4 REs/srA/vfs /N Masa/ws 1L E h CAPAc/TA/vcf //v M/moM/moFA/PADS TZ -E- 5 f4 V V4 V X w 7% 9/ 92 SYM) ATTORNEY all the digits of a chosen notation.

Patented Mar. 14, 1950 UNITED STATES PATENT OFFICE DESCENDING COUNTER York Application August 13, 1947, Serial N0. 768,393

lfiClaims. l

This invention relatesrto electronic 4counters and its general object is to .provide a directsubtraction electronic counter.

Prior art electronic counters are adding counters which may .perform subtraction indirectly by addition of complements. Preliminary conversion of asubtrahend to .itsA complement 4must be made and the numberfoi pla-'ces in theoomplement must be equal to the number :of orders of the counter. Thus, to .subtract 1 from a twoordercounter, the complement 99 must be `added to the counter. `Entry of Ya value in :an electronic counter is usually effected by application of a number of pulses equal to Vthe-Value to be entered. So, `to enter complement '99, ninetynine consecutive pulses would have to be applied to the units order. If an accumulator type of counter, is used, each order .has its own input circuit, but the problem,:of carry between orders is more complicated .than kfor straight counters. In any event, to enter complement 99 into an electronic accumulator, at least nine pulses would have to be applied to each order.

In contradistinction, the present ,invention provides an electronic direct vsubtraction counter which subtracts a number :directly and. not by addition of .its complement, Further, the invention provides an electronic direct subtraction counter which subtracts a value in response to application of a number of :pulses equal tothe value; e. g., it Ysubtracts 1 ,in response to application of but a single entry pulse. The resulting gain in speed of subtractive .calculationvbysuch direct subtraction felectronic `counter over the speed of such calculation by an addingfelectronic counter is considerableandzis highly important since the essential reason Vfor employing electronic calculating devices is to eiect calculations at high speed.

The invention is .embodied in an electronic counter of the type having in each complete order a series of .electronic stages to manifest Adding counters which subtract by addition of complements require as Imany complete orders as the nuznber of places inthe minuend. 'The present incompletefsince it needs only enough stages to manifest 3.

A feature .of the A.invention is aicarrycircuit between ordersof:the.electronicfcounter for ei- .iecting a subtractive `carryoi 1.to one order as result of itslowerordenhaving steppedirom the lowest .to thehighest digit .manifestatiorn e...g. if the decimalnotationis used,.subtractive (c1. zes-92) carry .of 1 to A'a higher order will occur upon the lower order stepping'from l0 to 9.

Another -feature of the invention is a circuit operated under controloi the orders ot the elec- .tronic counters for signaling a zero remainder.

Theinvention further provides a direct subtraction `electronic counter of the vbinary decimal type, the stages yof a complete order relating'to powers of 2 and being coupled in general .binary fashion but -supplementedby circuits for transposingoperation ironia binary basis to a decimal subtraction cycle basis. Thus, each complete order .will yhave a descending value cycle of `ten steps.

rllhe invention .also has for an object the provision of-means to apply a number in binary term form directly to a binary. decimal electronic counter or register.

,More specifically, according tothe invention, a number in binary `term form is yto be .applied by individually operating the stages of each order in accordance with the binary terms in the number. Thereafter, stepping vof the Aorder is to be effected "by .applying entry pulses'to an input of the order `to causezinterrelated operation of the stages.

yOther objects ofthe invention will be .pointed out inthe following vdescription and claims .and illustrated in theaccompanying drawings, which disclose, by way .of examples, the `principle .of thefinvention andthe best mode, .which has been contemplated, of applying that principle.

-In the drawings:

Fig. 1 is-acircuit View of an electronic trigger employed .in the invention.

Fig. la is a block diagram of the trigger.

Fig. 2 is a sequence chart of the preferred embodiment.

Figs. 3a and .3b .illustrate Vthe .circuit of the preferred embodiment.

Fig. .4 illustrates .the circuitof a modification of .a complete order.

Fig. .5 is .asequence chart pertaining to the IFig. Ll-circuit.

Voltage lines B, D,G, BI and N are supplied `from a suitable source ,with voltages indicated Ain Fig. .1. .Another voltage line CBI derives voltage .from line .BI .while switch I 5 remains closed. Typical constants are indicated in the circuit 50 views vbut .it is -understood .these maybe Vwidely varied. without altering the substance of the invention. Resistance values are given in megohms and -capacitance `values in micromicro- .farads The triodesare'halves of tubesof type 55 12SN7 and the pentodes are of type BSK'?. Fig. l

shows thecircuit of an electronic trigger of a type fully discussed Ain .application Serial No.

569,992-oi' Palmer and Phelps, iled .December 27,19%. -Briefly,-this trigger 'includestwo ret- '60 roactivelycoupledftubes'-mand H. The trigger has two relatively opposite stable states. In one state, here called the oi state, tube il] is conductive and its anode terminal f is at about G volts, While tube il is non-conductive and its anode terminal c at about 150 volts. In the opposite state, here called the on state, tube ifi is non-conductive and point f at about 150 volts while tube l! is conductive and point c at about 50 volts. Upon reversal of the trigger from oir to on state, there is a steep drop in potential or negative impulse of about -50 volts at midpoint d of the anode resistor Hr of tube H. It is characteristic of this trigger that it is considerably more sensitive to applied negative impulses than to similarly applied positive mpulses. In the present case, a negative impulse of about -50 V. applied to the trigger input terminal a or h or concurrently to both is more than sufcient to reverse the trigger but a similarly applied positive impulse of such amplitude is not eiiective to reverse the trigger. Reversal of the trigger also may be controlled by an auxiliary circuit operable to draw current through anode resistor IGT or l l1' so as to depress the potential at the terminal c or f to about 50 volts. Thus, if such auxiliary circuit be connected to point c and operated, while the trigger is off, to draw current, then the circuit will cause the trigger to turn on but if at the same time another auxiliary circuit connected to point f is drawing current, then the latter circuit will lock the trigger in off state. When, as in Fig. l.. the grid of tube Il is coupled to line BI and the grid of tube Il! to line CBI. the trigger may be reset to 01T state by opening the switch l5 to remove negative potential from line CBI. In consequence, negative bias is taken off the tube l, causing the trigger to go off. When the grid of tube H is coupled to line CBI and the grid of tube Il) to line BI. the trigger is reset to on state upon opening switch I5.

In the circuit views (Figs. 3a, 3b and 4), letter :c adjacent a tube denotes its stand-by conductive or on condition, letter :r at the right side of the block diagram of a trigger denotes its stand-by off state, and letter :c at the left side of the block diagram denotes stand-by on state, In the sequence charts (Figs. 2 and 5), on status of a tube or trigger is denoted by a heavy line and off state by absence of such line. oi. a multi-grid tube by removing cut-oi bias from one ci its grids so that it may be subsequently switched on by also removing cut-off bias from another of its grids. is denoted in the cycle charts by a sectioned line.

Figs. 3a and 3b show a two-order counter of preferred form and Fig. 2 is the sequence chart for this counter. A complete order includes four stages, each consisting of a trigger T. The four stages are designated TI, T2, T4, and T8 to indicate the values 1, 2, 4 and 8 which they manifest respectively when in on state. It may be noted that these values correspond respectively to the binarv terms 20, 21, 22, and 23. If all the stages are oi, the order stands at 0; if Tl alone is on, the order is at l; with TI and T8 on, the order is at 9, and so on. As illustrative, the tens order includes only stages TI and T2, limiting the minuend capacity of the counter to no greater than 39.

Tubes I in each order sense zero status of the order. The units order has four such tubes Il, I2, I4 and Iii having a common anode line 22u. The tens order has two tubes Il and I2 having a common anode line 22t. The grid of each tube Conditioning l I is resistance-coupled to point f of the correspondingly numbered stage in the same order. When the trigger is on, point f is at high potential, so that the associated tube I is on and its anode line is at 10W potential. When the trigger is off, point f is at low potential and the related tube I is oli?. All the tubes I in an order are ofi only when the stages of the order are all oiI and, hence, when the order is at zero. Under this condition, the common anode line of the tubes I in the order is at high potential. Ii only a single order counter is used, then the high potential on line 22u will serve as a signal. of a zero remainder on the counter. If two or more orders are used, then means are provided to be jointly controlled by the zero sensing means of each order. Thus, in the present case, a pentode Z (Fig. 3b) is provided which has its control and suppressor grids respectively and suitably coupled to lines 22u and 22t. When the tens order is stepped to 0, it conditions Z to go on upon the units order later stepping to zero. As Z goes on, it produces a negative output pulse signaling zero remainder.

The counter is to be stepped in response to negative entry pulses on input line 2l connected to points a and h of Tl in the units order. The stepping must be effected in descending direction upon a decimal count cycle basis. This means 'that in each complete order, here the units order, the manifestations O, 9, 3 1, 0 are to be produced successively in response to ten successive impulses, assuming the order starts in zero status. The required operation is obtained in the embodiment under discussion by unique coupling between the stages and by special supplemental circuits including the zero sensing circuit of the units order. The coupling between stages is from point d of Ti to points a and 7L of T2, 'from (Z ci T2 to c and h of T4, and from d of T4 to ay of TB. Each time a stage T goes on, it produces a sharp negative impulse at its point d. This impulse transmitted to c and h of another trigger is ei'iective to reverse the latter unless its reversal is blocked. Since d of Tf1 is coupled only to terminal a of T8, the negative impulse at ol (T4) can serve merely to trip T3 from on to oi state. When a stage goes off, it produces a positive impulse at its point ci but this impulse transmitted to a or 7i or both of another trigger is ineilective upon the latter for the reason previously explained. Conning the explanation for the present to the complete, units order, assume it is at Zero, all the stages being off. The first subtractive step must turn on Tl and TB to manifest 9. But When TI goes on, it attempts to turn on T2 and this action must be blocked at this step. This is accomplished under control o the zerol sensing circuit of tubes I and a blocking tube X. The anode of X is tied to point f of T2 and the grid of X is resistance-coupled to line 22u which is at high potential only in zero status of the order. Accordingly, tube X is on only when the order is at 0. With X on, it prevents the anode point f (T2) from rising above about 50 volts, thus locking T2 in oii status. Not only must T2 be prevented from going on upon the rst step from O of the order, but T8 must go on to combine with Ti, also to be turned on, for manifesting 9. T8 is turned on under control of a pentode switching tube W which is conditioned by the Zero sensing circuit when the order is at zero and is rendered conductive in response to Ti being turned on upon the first step. To this end, the anode of W is resistanceupon the controlgridebeing impulsedabove criti cal potential. `WhenWgoes on,: it develops a negative irnpulsezsuponits-i anode which isftransmitted to vpoint h of'TS. to turn it on.

, Aicornpiete steppingcycleof the'vcompleteaunits f orderfrom 0 back to Owill now tbe describedwith reference to Figs. 2, Brr-and 3b; vThezlirstientry pulse turns.` on .TL vAs Ti turns oniit' produces a steep negative .pulse at point d which attempts. to turn on T2. n because it is locked inoff state bytubeX which But 'I2-does not turnV on now remains conductive until @the negative: pulse at dCIi) is spent. Furthenlas Tl ygoestornzitproduces a steep positive pulse at its `point yp-which` f pulse is capacitatively transferred tothe acontrol grid of now-conditioned tube W. Thereupon rW becomes momentarily conductive to apply a`nega- L ytive pulse to` point h. of T8, turning it on. When Tl is turned on, it also renderstube Il conductive` to removeV high potentialfrcmline 22u,nthus allowing `tube X 'to become non-conductive and causing tube W to be vde-conditioned.- However,

the tubes X and W will .accomplish theirziunctions before 1ine`22u rdrops to ylow potential. This is accounted for by the sharpness 'Lof thepulses which appear at points d and f offTl as it turns 2.011,1.andutherelation OYRC factorsgof the circuits of Il, X and W. This relationiswsuch that 'tube W is not de-conditionedand` tube X` is not turnedc-i until after the negative pulseat d(Tl) has been spent and the positive pulseat ,KTD has turned on W to trip' T8 on. Further delay in turning on Il may beobtained-by iadditionally coupling the grid of Il `through a` capacitor `CI vand resistor RI to point c of TI, as indicated in dottedlines in'Fig. 3a. lisTi'goes on, its point c drops in potential .While-pointv f rises in potential. `The eifect. on tube Il of the drop at cof Tl` is opposite tothe eilect on` Il of the rise at f of TI so that Il` `remainsoii for an interval governed by the RC time factor of the connections between the grid of `Il yand point c of TI.

'The foregoing :has explainedthe subtractive step of the complete, units order fromI Oto 9 in f .response to the: rst entry pulse. "The second enrtry pulse trips'Tl off and with T8 alone'on, the order is at 8.` The third pulsetrips Tl on, which nowis effective'` tov switch vT2 on. As T21" s.

`goes on, it trips T4` on, and T4,in turn,1switches T8 off. The order vthen stands at '7,1TI, T2 `and 'T4 being on. The fourth pulse trips TI oil and l `as T2 and T4 remain on,the order is at 6. The lilith pulse switches 'TI on which causes T2 to lgol' 1 01T. Since TI Yand T4 `now are on, thev ordervis at 5. The sixth pulse turns oi TI 'and T4 re- :mains on to manifest 4. lTheseventh pulsey trips Tl on `which causes T2 to go on and switch "T4 off, so the order thenVV stands` at 3." The Veighthv pulse turns off Tl and' T2 alone is now on, :so

' that 2 is manifested. The ninth pulse trips" Tl on which causesTZ to be switched off, so the order now manifests 1. The tenth pulse turns off TI, and the stages are all olii so the orderl is back tofzero.

When the units order is stepped from Oto 9,

it exceeds itsvsubtractive capacity and carry must be eiected to the tens-order. The'turningy onor 1. `of T8 .may beg-,utilized to. control carryfto nthesnext @fordernV For thispurpose, point d of T8 iscoupled .tofpoints aand h of Tl inthetens order. When @T8 turns on, 'the resulting negative'pulse at its i. point d1acts upon points a and h of Tl inthe tens :thereupon itfwill reverse T2.

Assume, for in- .;.estance 'that minuend 3 is in the tens order,xso that its l,stages Ti .and T2 are on. The'rst carry pulse turns oi Tlleaving 2 standing in the `tens reorder. lThe secondcarry pulse turns `on TI which -1,.t urns.off T2, leaving 1 standingin the tens order.

v vThe third carry pulse turns on" Tl and the tens rordergis thenat 0. Itrnay be noted that the invcomplete tens order vdoes not require tubes X and because an incomplete order, by reason of the y.unique couplingbetween stages Tl and T2 and ,febetween `I'Zeand if a third stage be included, .operatesiny descending count direction o-n a pure v..combinational binary term manifesting basis.

The tubesI X. andW along Vwith a set of tubes I .arefgrequired only for-each complete order vci four stages so as to'cause it to operate in descending account direction on an over-all ldecimalcount cycle y-.basis .1 The tensvorderwill reach aeroxstatus `before Thus, if the minuencl 19y has .pulses Wllstep theunits order from 9 back to 9 y.in descending countdirection. On the tenth step, .whenthe-.units order goes from Oto 9, it applies :a carry'pulse to the tens order, turning oil 'Ti in the tens order.

.As the tens order now is at -Zer.o,\.its tubes Ii and I2. are both/oit line is,` at" high potential, conditioning tube Z. vThe ,.:neXt nine 4entry ypulses reduce the manifestation potentialto turn on conditioned tube Z to produce the `zero remainder signal.

. 'Tnet-means for entering a minuend will be de- ;scribed next. Minuend entry is most efficiently ."done,herefby-individually turning on the stages f ofthe counter according to the binary terms l, 2,

minuend entry render it unnecessary to Zeroize rfthecounter prior to lminuend entry, as would be w necessary in vordinary counters.

Here, the minufend entry means substitutes the minuend for any other number which may be previously standing ...inthe-counter.

j lIn;v applying a rn-inued to ythe counter by indi- .circuits must `be overcome. 60.."

Thus, during minuendapplication,r the turning onof Tl l(units order) shouldfnot, through W, turn on Til; ne turning :on of Tshould not produce a carry to the tens order; the turning on ci T in the tens order Should.notturn on Tin thetens order; and the ,Y turning on of TZin the units'order must be done after' itis released by tube and must then not fzturn-on T4. i Themeans disclosed herein for ap- `:plying the minuend solves these problems and includes sets ofthree minuendinput tubes P, S, and V, Vone vsetV fory each stage in the counter. The

'orders yto Whichtheyrelate. "Thus, in the units iiorder, P4, Strand Vlarefgthetubes of the 'set related. to stageT4 intthe unitsorder.

There are four minuend input lines Ll, L2, L4 and L8 for the units order and two input lines Ll and L2 for the incomplete tens order. Suitable means which need not be shown here are provided for selectively applying high potential to the lines L according to the binary terms in the digits of the minuend to be entered. For cxainple, if the minuend digit to be introduced in the units order is 6, lines L2 and Lil in this order are placed at high potential. Each line L similarly controls a corresponding stage through the related set of minuend input tubes P, S, and V. Considering the units order, line L2 controls stage T2 through tubes P2, S2, and V2. The line L2 is resistance-coupled to the control grids of P2 and V2. When L2 is at low potential, these control grids are below critical voltage and block the tubes P2 and V2. When L2 is at high potential, it brings the control grids of P2 and V2 above critical voltage, thus rendering V2 conduc tive and conditioning P2 to become conductive when its suppressor is raised above its normal cut-ofi voltage. The anode of V2 is resistancecoupled to the control grid of S2. When V2 is non-conductive, its anode is at high potential and the control grid of S2 is above cuteoff bias, conditioning S2 to become conductive when its suppressor is raised above its normal cut-off potential. But when V2 is conductive, its low anode potential de-ccnditions S2 to prevent it from becomingr conductive. It has been explained that When L2 is at high potential, it conditions P2 and renders V2 conductive which, in turn, de-conditions S2. But if L2 is at lovv potential,

P2 is not conditioned and V2 is not conductive, :1

so that S2 is conditioned. Thus, one or the other of tubes P2 and S2 is conditioned but not both at any one time. The anode of P2 connects to point c of T2 and the anode of S2 connects to point f of T2. When P2 or S2 is not conducting, it has no influence on T2. Tf P2 is conducting, its anode potential drops to about 50 volts, depressing the point c to this potential, so that T2 turns on. Ii S2 is conductive, then its anode potential is about 50 volts and blocks T2 from turning on. Since only P2 or S2 but not both are conditioned, only one will become conductive upon minuend entry to exert its control over T2.

Similarly, in each set of minuend input tubes, either P or S but not both will be conditioned to become selectively conductive so as selectively to cause the related stage to turn on or prevent its turning on.

To enable minuend digit 2 to be applied to a complete order, means are provided to render tube K non-conductive so as not to lock T2 in ofi state during minuend entry. For this purpose, a control tube K is included in each coniplete order. The anode of tube K is tied to the common anode line 22u of tubes I in the complete order, here the units order. Upon entry of the minuend, the tube K will be rendered conductive, insuring line 22u being at low potential, so that tube X will be rendered non-conductive and in efective to lock T2 in off state. Also tube W will be cle-conditioned to make doubly certain that T8 will not be turned on as a result of Tl being turned on during minuend entry.

The snppressors of all the tubes P and S and the grid of tube K are resistancecoupled to a common line 25 which is normally at lovv potential, under which condition the Suppressors of P and S and the grid of K are all below critical potential. When the minuend entry is tobemade, a positive pulse from a suitable source is impressed on line 25, increasing its potential to such extent as to cause the Suppressors of P and S and the grid of K to rise above cut-of! potential. Tube K thereupon becomes conductive to produce the effect described above. The conditioned ones of the tubes P and S also become conductive to selectively turn on or suppress turning on of the related counter stages.

To take a concrete example, assume minuend 13 is to be entered in the counter. High potential is impressed on lines Ll and L2 of the units order and line Ll of the tens order. Accordingly, in the units order, Pl and P2 are conditioned and Vl and V2 are conductive to de-condition Si and S2; in the tens order, Pi is conditioned and VI is conductive to de-conditicn SI. The remaining P tubes remain yrin-conditioned and the remaining S tubes remain conditioned. At a later time, a positive pulse is applied to line 25. For the effective duration of this pulse, line 2t* is at high potential, causing the conditioned ones of tubes P and S and also the tube K to become conductive. In the units order, PI is conductive and turns on TI also P2 is conductive and turns on T2 which has been released for such action as a result of K having been rendered conductive. When Tl turns on, it normally acts through W to turn on T8. But with iff now conducting it de-conditions W so that it will not respond to the turning on of TI and therefore will not attempt to turn on T3. In any event, T3 will not turn on because, in the chosen example, S6 is conductive and locking T3 in off state. In the units order, T2 has been turned on and normally would turn on T4 but since S4 is now conductive, it prevents T4 from turning on. In the tens order, Tl has been turned on and attempts to turn T2 on but as S2 in this order is now conductive, T2 will not turn on. It is to be noted that tube K, while its primary function is to prevent tube X from locking T2 in on" state during minuend entry, has the further advantage of allowing a shorter min-uend entry timing pulse to be used since it causes immediate drop in potential of line 22u, placing the order immediately in condition for proper individual switching of the stages according to the minuend to be applied. In other Words, tube K makes possible faster minuend entry and also correct minuend entry.

Fig. l illustrates a modification of a complete order of direct subtraction counter. A sequence chart of its operation is shown in Fig. 5. The elements of this modification which correspond to elements of the previously described embodiment are given like reference designations. Counting stages TI, T2, T4 and T8 are coupled to one another as in the first form. The means for transposing binary type operation of the counter order to a decimal cycle basis include three triodes I2, Il?, and I8 which are coupled to stages T2, T4 and T8 as in the first embodiment. The blocking tube X is coupled to T2 also as in the -rst embodiment but is controlled by tubes I indirectly, through control tubes 9| and S2 and a trigger TA. The pentode W is coupled -to stage T8 as in the first embodiment but is conditioned by a trigger TA to be turned on by stage Tl when the latter is tripped on by the rst entry pulse received after the order is at zero.

A minuend digit may be applied in a suitable 1 manner as, for instance, in the manner explained `mier the first embodiment. Let it be assumed the arsoozezif Y order stands at2. Under this condition, T2 is on, TI; T4` and Tiare off, I2is conductive and I4 'and I8`are non-conductive. i With TI oi, its points .c and if areat relatively highv and loW potentials. Point c of T! is suitabl-ycoupled to the controlgrds of tubes -SI and 92=and since point c is at high potential, these control grids are now above`-` blocking bias. Point v NT!) is coupled to the control-grid oftube W and since this point f nowis at low potential, the control grid of W is at blocking bias. T8 is coupled tothe suppressor ofrfi and since TS now is off, its point f and the suppressor of 9| are at low potential. Hence, although ifis at high control grid potential, it remains nonconductive because its suppressor is at low potential. As the tube I2 is conductive, the common anode line 22 or tubes I- is at low potential. Line 22 is coupled to the suppressor of 92 and being at low potential, it maintains the suppressor at low potentiaLisovthat Afifremains off despite its high `control grid potential. Point f of trigger TA is coupled to the grid of tube X and the suppressor of tube W; With the order novi at TA is off andits point f' at lou7 potential, so that X is now oi and the suppressor oi W is at blocking potential.

The next entry pulse on input circuit 2i trips v Ti cn, which causes T2 to go ofi. The order now stands at l. With TI on, its point c is at low potential andl its pointf at high potential. Therefore, the control grids of Si and 92, con-v neoted to point c(T|) arenowat blocking po-` tential, while the control gridof W, connected to point f Tl is above blocking potential. Since T still is oi, its-point f and the suppressor of 9! remain at low potential. When Til turned on?, it rendered I2 non-conductive; all the tubes I now are non-conductive, allowing line 22 to rise to high potential The suppressorof Q2 therefore is driven above blocking potential, but 92' does not become'conductive because its control grid'novv isy at low potential. Trigger TA reinains in off state.`

The following entry pulse turns oil" Tl All the stages now are ofi and the vordervstands at 0. As TI trips off, its point c rises'in potential, returning the control grids of -91` and S2 to a potential above cut-oival-ue. YTube 9i still does not conduct because its suppressor is still at blocking potential. In the preceding step, vthe suppressor of 92 wasraisedabove blocking potential. New, When-the order steps from l to 0, the control grid of $2 alsois raised in potential. Accordingly, SE'becornes conductive and applies a negative, tripping pulse to point It of TA, turning it on. As TA goes on, its Apoint f rises in pof tential, thus rendering tube-X conductive and conditioning tube W.` Tubey X noW is effective to lock T2 in oi state.

The next entry pulse turns on TI. As Tl goes f on, it tends to turn on T2 but the latter now is locked in off state by conductive tube X, Further, as TI goes on, its point j rises in potential and drives the control grid of WY above blocking potential. on statusof TA in the preceding. step, therefore becomes conductive, producing a negative, tripping pulse which turns on T8. The order nowv stands at 9, Tl'and Tbeing on. With T8 on, I8 is conductive a-nd line 22 drops in potential, as does the suppressor of tube 92;: Further, with T8 on, Yits point f is at high potential, as is the connected suppressor :of ltube 9|: Hence tubeiSl, but not tube 92, is conditioned v.torespond to the The point f of v Tube W, having been conditioned by" 1G next turning oit of T I. Still further, as T8 turned on, `it produced a negative carry pulse at its point diorcausing a carry-tothe next order, as in the first embodiment.

rThe nextentry pulse turnson Ti; T3 remains on, so-the order manifests As. Ti turns off,

its 'point c risesv inpotential, .as the. control grid of conditioned tube Accordingly, @l becomes conductive, developing a negative tripping pulse ivliichz is applied to point c of TA .to turn .Tu-v WitiiTA oil', its point fis at low potential; so thattuoe X is now non-conductive andr tubel/Vis'nov/ defoonditioned. As 'tube is nonconductive, vit-releases Tiior ori-switching at the next step.

Thefother steps inthe sequence may be oilowed through readilyv with the aid of Fig. 5.

Itis clear that they modiiied complete order shown iii-Fig. 4 diiiers from the embodiment shown in 3 in the means for transposing count descending operation for theorder from a binary basis sofa decirnai cycle basis.

While there have been shown and describedr and pointed out the fundamental novel features of the inventionas applied to a preierred einbodiinent and a modincation, it will be undere` stood that .various omissions and substitutions and changes in the several forros and details oi the devices illustrated andin their operation may bemade by those skilledy in the art,I Without departing. from theY spirit of the invention. It is the intention, thereiore, to beA limited only as indicated'bythe scope yoi `the foliowing claims.

What is claimed is:

l. A direct subtraction'electronic counter including a denominational' order network oi' trig gers fewer than'the number oi: digits in the tens notation and.SerV-ingsingly and in combination, by their selective states, toinaniiest seiectiveiy the different digits or" the tens notation, means to apply a minuend digit to the netvvork'oi triggers, a circuit forapplying to the network successive pulses representing the true value o a subtrahend, and circuits coupling thetriggers for `response to said pulses in descending count se quence so as to diminish the minuend digit by the subtrahend, saidcoupling circuits means conditioned by thetriggerswhen manifesting zero for operating, upon application to the V'series of triggers of the next pulse, to reset the triggers to a manifestation ofinine.

2. A descendingelectric counter including a binary decimal group of-1, 2, 4, and 8 electric triggers, each having alternative stable on and of electricaly states, to nianiiestsingiy and in combination by their onstates the values il to 9, said group having fewer triggers than the nun ber of `digits in the decimal notation, a circuit for applying input pulses to the l trigger, each pulse reversing this trigger; circuits coupling the triggers in generally binary: counter'iashion for descending .counter sequenceof reversals in state inresponse to the .reversalsofnthe l trigger, said coupling circuits including supplemental means for transposng operation or the group of 75 coupled to the 1 trigger to be operated thereby.

including after being conditioned, when turned on by an input pulse for producing a pulse to turn on the 8 trigger', so that the group of triggers manifests 9 after manifesting 0.

4. An electronic register including a group of electronic triggers, each having alternative stable states, for selectively manifesting according to theil` states the digits of a chosen notation, circuits coupling the triggers for interrelated reversals in state in response to pulses applied to the group so as to receive entry of a digit dependent on the number1 of applied pulses and to change the digit manifestation accordingly, and means for applying a digit directly to the group of triggers, said means including circuits for rendering the coupling circuits ineffective and for applying potentials to the triggers selectively to reverse them individually and independently to set them' in states for manifesting the applied digit.

5. An electronic register including a group of electronic triggers, each having alternative stablev states, for selectively manifesting according to their states the digits of a chosen notation, circuits coupling the triggers for interrelated reversals in state in response to pulses applied to the group so as to receive entry of a digit dependent on the number of applied pulses and to change the digit manifestation accordingly, and means for applying a digit directly to the group of triggers, said means including for each trigger a tripping circuit operable to apply potential to the trigger to reverse its state and an opposing circuit coupled to the trigger and operable for blocking the reversal of the trigger, and means for selectively rendering the tripping circuits and the opposing circuits operable in accordance with the digit to be applied to the group of triggers, said opposing circuits `preventing the triggers from being reversed by potential derived through the coupling circuits.

6. A direct subtraction binary-decade counter including a denominational order network having four inherently binary triggers connected in series chain, each trigger comprising nrst and second grid controlled tubes and having on and oi states; means for entering a minuend in said counter in binary form; a connection from the grids of the tubes of the first trigger to a source or pulses used as subtrahend entries; four trigger status sensing tubes, one for each of said triggers, and each having its control grid connected to the plate oi the second tube of the corresponding trigger so that it is conductive when its corresponding trig ger is on and non-conductive when its corresponding trigger is off, a remainder line connecting the plates of said four tubes, so that said line is at its highest voltage when all said triggers are ofi; a blocking tube having its plate connected to the plate of the second tube of the second trigger and its control grid connected to said line, to be plate current responsive to the highest voltage thereon so as to lock the second trigger off; a multi-grid switching tube having one grid connected to said remainder line and one grid capacitively coupled to the plate of the second tube of the first trigger so that the highest voltage on said line conditions said multi-grid tube and the tripping of the iirst trigger to the on state renders the multi-grid tube conductive, and a connection from the plate circuit of said multi-grid tube to the control grid of the second tube of the fourth trigger to trip it on when the switching tube is rendered conductive, whereby said tripping on of the iirst trigger steps the counter from its lowest to highest digital capacity.

7. The counter of claim 6 wherein said means for entering a minuend includes first, second and third electron tubes and a minuend input terminal for ealch of said four triggers; connections from the plates of said rst and second electron tubes to the plates of the rst and second tubes, respectively, of the corresponding trigger so that conduction through the first electron tube trips the trigger on and conduction through the second electron tube locks the trigger off; a connection from said input terminal to a grid of said first tube and the control grid of said third tube, a connection from the plate of the third tube to a grid of the second tube, so that the second tube only, is conditioned, when the third tube is nonconductive and the first tube only, is conditioned, when a positive voltage is applied to the corresponding input terminal to render the third tube conductive; a control tube having its plate connected to said remainder line to decrease the voltage thereon when said control tube is conductive to render said blocking tube non-conductive; a source of positive pulses connected to a grid of said control tube and to a second grid of said first and second electron 'tubes and applied subsequent to each application of pulses to the minuend input terminals to render the control tube and said rst electron tube conductive, the conduction of said control tube rendering said blocking tube non-conductive and to de-condition said switching tube thereby insuring that the fourth trigger will not be tripped on when the rst trigger is tripped on.

8. The counter of claim 6 including a plurality of similar denominational order networks connected in series chain, the subtrahend entries for each higher network being supplied only by the next lower network when it is tripped from its lowest to highest digital capacity; a multi-grid tube for signaling a zero remainder and having one grid connected to the remainder line of one order and another grid connected to the remainder line of another order so that it is rendered conductive only when there is zero remainder in each of the two orders.

9. A direct subtraction binary-decade counter, including a denominational order network having four inherently binary triggers connected in series chain, each trigger comprising two grid controlled tubes and having on and off states; bias means for placing all triggers in the off state at starting; means for entering a minuend in said counter in binary fashion; a connection from the first trigger to a source of pulses used as subtrahend entries; second, third and fourth trigger status sensing tubes each having their control grid connected to the plate of the second tube of the corresponding trigger so that it is conductive only when its corresponding trigger is on; a remainder line connecting the plates of said sensing tubes in parallel so that said line is at its highest voltage when all said corresponding triggers are off; a fifth trigger circuit in the on state at starting; iirst and second multigrid `control tubes, said first tube having one grid coupled to the plate of the rst tube of the rst trigger, another grid coupled to the plate of the second tube of the fourth trigger and its plate coupled to the grid of the first tube of said fifth trigger so that said iirst tube is conductive only when the iirst trigger is off and the vfourth trigger is on simultaneously to trip said fifth trigger oii' and said second tube having one grid coupled to the plate of the first tube of the first trigger, another grid coupled to said line and its plate coupled to the grid of the second tube of said fifth trigger so that said second tube is conductive only when the first trigger is off and the status sensing tubes non-conductive simultaneously to trip said fifth trigger on; a multigrid switching tube having one grid lcoupled to the platev of the second tube of said fifth trigger, another grid coupled to the plate of the second tube of the first trigger and its plate coupled to the grid of the second tube of the fourth trigger so that said switching tube is conductive only when the first trigger is on and said fth trigger is on simultaneously to trip the fourth trigger on; a grid controlled blocking tube having its plate connected to the plate of the second tube of the second trigger and its control grid coupled to the plate of the second tube of said fifth trigger so that said blocking tube is conductive when said fth trigger is on to lock the second trigger olf. l

10. In a direct subtraction binary-decade counter including a plurality of denominational order networks each having four inherently binary triggers connected in series 'chain and each trigger having on and olf states; means for entering a minuend in said counter according to binary notation; means for applying subtrahend entries to reverse the state of the first trigger; a sensing tube operated by each trigger to be conductive only when the trigger is on; a remainder line having a potential thereon under combined control of said sensing tubes; a blocking tube controlled Iby the potential on said line to lock the second trigger off when said sensing tubes are all non-conductive; a switchingtube responsive to said line and the first trigger; means coupling said switching tube to the fourth trige ger to effect a tripping thereof to change the digital capacity of the counter from its lowest to highest value.

11. In a binary-decade counter including a denominational order network of four inherently binary triggers connected in series chain and having two stable states alternately assumed; bias means for placing said trigger in a preselected stable state; means for applying subtrahend entries to trip the first trigger from either stable state; electronic tube means responsive only iwhen said network manifests a zero remainder and the first trigger is tripped from the preselected state to trip the fourth trigger from the preselected state to render said network responsive in descending count sequence to subsequent subtrahend entries; first, second and third minuend input tubes for each trigger; means for applying minuend entries to said input tubes according to the binary notation to trip the corresponding trigger; and a source of pulses applied subsequent to each minuend entry to disable said electronic tube means.

12. The direct subtraction binary-decade counter, including denominational order network having four inherently binary triggers connected in series chain, each trigger comprising two grid control tubes and having two stable states; bias means for placing all triggers in a preselected stable state at starting; means for entering a minuend in said counter according to the binary notation; means for applying subtrahend entries to the first trigger; a plurality of trigger status sensing tubes and a line common thereto, said line having voltage thereon determined by the conductive condition of tubes; a fifth trigger;

a first control tube responsive to the first trigger and the fourth 'trigger conjointly to trip said fifth trigger from only one stable state; a second control tube responsive to the first trigger and to said line conjointly to trip said fth trigger to only said one said stable state; a switching tube re sponsive to said fifth trigger and the rst trigger conjointly to trip the fourth trigger to only one stable state; and a blocking tube responsive to the second trigger and said fifth trigger conj ointly to lock said fifth trigger in only one stable state when the second trigger is in the other stable state.

l". A descending electronic counter including a plurality of carry-related denominational order networks of electric space discharge devices variably energized by applied potential to manifest selectively different digits of a notation; each network having an input circuit for applying pulses representing the direct value of a subtrahend to the network, and circuits coupling the discharge devices for interrelated descending count sequence of changes in energization in respense to the applied pulse to subtract said direct value from the digit previously manifested by said devices, said coupling circuits including means to compel the devices when energized for manifesting zero to change to a manifestation of the highest digit of the notation in response to the next applied pulse' a circuit yfor signaling a zero remainder in the counter; and a plurality of circuits, each conditioned by a related order network when in zero status, for collectively operating to render said signaling circuit elective when all said order networks are brought to zero status.

14. An electronic binary-decade counter setn table with a minuend amount and capable of direct subtraction and including a denominational order series of electronic triggers fewer than the number of digits in the tens notation and serving singly and in combination, by their selective states, to manifest selectively the difn ferent digits of the tens notation, a circuit for 45 applying to the first trigger in the series input vpulses representing the true value of a subtrahend, each pulse reversing this trigger, circuits coupling the triggers of the series in binary counter series chain for response to the input 50 pulses and the reversals of said rst trigger in descending count manifesting sequence until the series of triggers manifests zero, and means for 'transposing operation of the series of triggers from a binary counting basis to a direct subtrac- 55 tion decimal basis comprising electronic tube means conditioned by the series of triggers when manifesting zero for operating, upon the application to said first trigger of the next input pulse and the reversal of the rst trigger by this next 50 pulse, to reset the series of triggers to a, manifestation of nine.

BYRON E. PHELPS.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,402,988 Dickinson July 2, 194.6 2,402,989 Dickinson July 2, 1946 2,428,990 Rajchman Oct. 14, 1947 2,442,428 Mumma June lJ 1948 

